Genotyping of Chlamydophila abortus strains by multilocus VNTR analysis

Abstract

Chlamydophila (C.) abortus is the causative agent of ovine enzootic abortion with zoonotic potential whose epidemiology has been held back because of the obligate intracellular habitat of the bacterium. In the present study, we report on a molecular typing method termed multiple loci variable number of tandem repeats (VNTR) Analysis (MLVA) for exploring the diversity of C. abortus. An initial analysis performed with 34 selected genetic loci on 34 ruminant strains including the variant Greek strains LLG and POS resulted in the identification of five polymorphic loci, confirming the widely held notion that C. abortus is a very homogeneous species. Analysis of additional 111 samples with the selected five loci resulted in the classification of all strains into six genotypes with distinct molecular patterns termed genotypes [1] through [6]. Interestingly, the classification of the isolates in the six genotypes was partly related to their geographical origin. Direct examination of clinical samples proved the MLVA to be suitable for direct typing. Analysis of the genomic sequences in six C. abortus prototypes of amplicons generated with each of the five selected VNTR primers revealed that variation between genotypes was caused by the presence or absence of coding tandem repeats in three loci. Amplification of Chlamydophila psittaci reference strains with the five selected VNTR primers and of the six C. abortus prototype strains with the eight VNTR primers established for the typing of C. psittaci [Laroucau, K., Thierry, S., Vorimore, F., Blanco, K., Kaleta, E., Hoop, R., Magnino, S., Vanrompay, D., Sachse, K., Myers, G.S., Bavoil, P.M., Vergnaud, G., Pourcel, C., 2008. High resolution typing of Chlamydophila psittaci by multilocus VNTR analysis (MLVA). Infect. Genet. Evol. 8(2), 171-181] showed that both MLVA typing systems were species-specific when all respective VNTR primer sets were used. In conclusion, the newly developed MLVA system provides a highly sensitive, high-resolution and easy-to-perform tool for the differentiation of C. abortus isolates of different origin, which is suitable for molecular epidemiological studies.